Quantification of petroclival exposure and surgical freedom as a function of temporal bony removal using frameless stereotaxy

Frank P.K. Hsu, Joseph Finiiio, Greg Anderson, Sean O. McMenomey, Johnny B. Delashaw

Research output: Contribution to journalArticlepeer-review


Introduction: In skull base surgery conventional wisdom conveys that more bony removal equals more exposure. However, this statement has not been quantitatively examined. In this study we employ the frameless stereotaxic system in quantitatively measuring the area of petroclival exposure and surgical freedom with each successive steps of temporal bone removal. Method: Twelve cadaver specimens were dissected using high-speed drill, under high-power magnification, in four predetermined and successive steps of bony removal: (1) removal of Kawase's triangle, (2) removal of Glasscock's triangle, (3) removal of cochlea and skeletonization of anterior internal auditory canal, and (4) inferior displacement of zygoma. Frameless stereotaxic system was utilized in measuring a standard set of parameters. These data were then utilized in the estimation of the area of the petroclival area exposed and the size of a spatial cone directed toward the clivus, which depicts the amount of surgical freedom available for manipulation for surgical instruments. Results: The initial step (1) offered 62 mm2 (SD = 43) exposed pertoclival area, with 84 mm2 (SD = 69) of surgical freedom. Subsequent removal of Glasscock's triangle (2) yielded 61 mm2 (SD = 22) of area and 76 mm2 (SD = 58) of surgical freedom. Further step (3) provided 128 mm2 (SD = 47) of area and 87 mm2 (SD = 87) of surgical freedom. The final step (4) yielded 135 mm2 (SD = 38) of area and 102 mm2 (SD = 69) of surgical freedom. Conclusion: The middle fossa approach provides a method of surgical exposure to the petroclival area. When examined quantitatively using the frameless stereotaxic device, the step involving the removal of cochlea and skeletonization of the anterior auditory canal provides the most significant increase in both exposure and surgical freedom. Removal of the zygoma does not appear to be effective in the improvement of surgical exposure and freedom. Bony removal in a surgical approach should be customized toward the underlying pathological condition.

Original languageEnglish (US)
Pages (from-to)21
Number of pages1
JournalSkull Base
Issue numberSUPPL. 1
StatePublished - 2001
Externally publishedYes

ASJC Scopus subject areas

  • Clinical Neurology


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